按SQL中的计算字段分组

I have written a query like this

我写了这样的查询

CASE 
              WHEN [col1] = 's' THEN '1'
              WHEN [col1] = 't' THEN '2' 
              WHEN [col1] = 'u' THEN '3' 
              WHEN [col2] = 'v' THEN '4'
.......
END AS product,
SUM(col3)
FROM dbo.TableA
C